Beyond the Milky Way (continued)
The peculiar galaxy Messier 82 (M82) is one of the most powerful infrared and radio sources in the sky. It forms a pair with its neighbor galaxy Messier 81 (M81). It is thought that a past, close encounter with the nearby galaxy M81 created turbulence near M82's core resulting in a heavy increase in star formation. M82 lies about 11 million light-years away from us.
The X-ray image of M82 reveals supernova remnants and high energy binary
stars. These are seen as the bright spots near the center of the image.
Many of the X-ray binaries are thought to contain a black hole. The
diffuse X-ray light is due to extremely hot gas flowing out of the galaxy.
The ultraviolet picture shows the strange nature of M82. The peculiar shape
is caused by obscuring dust on the foreground side of the galaxy. The
bright point-source seen in the lower right is a foreground star in our
Milky Way galaxy.
In the visible light image we can see the dust lanes within the central
regions of the galaxy. The reddish hue near the center of M82 is created
by the scattering effects of dust grains. Dust grains are more effective at
scattering short-wavelength blue light than long-wavelength red light.
This means that less of the blue light reaches our eye, leaving a reddened tint.
The radio image reveals the chaotic structure of the radiation emanating from
M82. The compact radio features are supernova remnants.
For additional images of Messier 82 at various wavelengths, visit
The Whirlpool Galaxy (Messier 51) is a face-on spiral galaxy gravitationally interacting with a smaller companion galaxy. It is about 37 million light years away from the Earth.
The X-ray image highlights the energetic central regions of the two interacting galaxies. Much of the diffuse glow is from multi-million degree gas. Many of the point-like sources in the x-ray image are black holes and neutron stars in binary star systems. Visible light clearly reveals the sweeping spiral arms and the fact that the arms include patchy knots of star formation. The companion galaxy, which is classified as an irregular galaxy, lacks the well-defined structure of a spiral galaxy and appears "attached" to the end of a spiral arm in the "Whirlpool Galaxy". Infrared is well-suited to studying star formation and tracing dust in spiral galaxies. The infrared image not only shows the galaxy cores and spiral arms, but nicely illustrates the knots of star formation occurring in the arms. The spiral arms extending from the galaxy center and the companion galaxy are clearly seen at radio wavelengths. A modest-sized red blob appears to be connected to the end of the southern spiral arm, located about the 8 o'clock position. This is probably a background quasar. For additional images of Messier 51 at various wavelengths, visit our Multiwavelength Gallery.
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